In plastic scintillator panels, gamma rays generate light pulses as they pass through the panel, and the energy of the light pulse is a function of the energy of the gamma ray. This energy dependent response can be exploited by digitizing the amplitude of light pulses from gamma ray captures and counting the pulses that fall into different energy ranges (also referred to as energy bins). Energy ranges are typically referred to as 8-bin “regions of interest” (ROI's) or 256-bin spectra. It is desirable for a scintillator panel to generate light pulses having approximately the same amplitude for gamma rays captured at any location in the panel. When the outputs of two photomultipliers (PMT's) disposed at opposite ends of a scintillator panel are summed, the panel output response is generally uniform. The exception to uniform response occurs when gamma rays intersect portions of the panel that are in close proximity to the PMT's.
What is needed is a scintillator panel and PMT assembly that provides substantially uniform output response, even when gamma rays strike the panel in close proximity to the PMT's.